The present invention relates to air heating apparatus and more particularly to an improved air heater of the portable type which is sound-conditioned and which recirculates air to and from a plenum chamber to be heated.
It is well known to utilize portable heaters to heat plenum chambers housing equipment and personnel in both military and commercial situations. In the past such portable heaters have often been both noisy and inefficient, the noises disturbing personnel who might be working or sleeping in the plenum chamber to be heated and a substantial amount of the heated air introduced from the portable heater into the plenum being wasted. The prior art has recognized the desirability of providing separate stationary compartments for an engine and powered equipment driven thereby, attention being directed to the following U.S. Pat. Nos.: 1,914,075, issued to J. W. Carl on June 13, 1933; 2,696,074, issued to J. Dolza on Dec. 13, 1933 and to Re. 29,923, reissued to Thien et al. on Mar. 6, 1979. The prior art has also recognized the desirability of utilizing radiator heat from a fluid cooled engine to heat ventilating air, attention being directed to U.S. Pat. No. 4,270,695, issued to Miles T. Carson on June 2, 1981. However, the prior art has not recognized the noise and wasted energy problems associated with a portable heater, let alone resolve these problems with a novel heating structure as disclosed hereinafter which is straightforward, economical and efficient in manufacture, assembly and operation and which effectively and efficiently utilizes recirculated air from the plenum which is heated by a heater arrangement that is sound-conditioned to minimize ambient noise.
Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure set forth hereinafter.